Magnetic-field-driven single-electron pump

A ferromagnetic triple-tunnel-junction device whose island electrodes or lead electrodes are composed of ferromagnetic metals with different coercive forces can be operated as a single-electron pump by applying an ac magnetic field. This device utilizes the magnetic-field-induced shift of chemical potential and magnetization reversal in the ferromagnetic electrode as its basic mechanisms in addition to the single-electron charging effect. We describe principle of its operation in terms of the orthodox theory of the single-electron tunneling, and further examine the role of the domain-wall propagation during the magnetization reversal in the operation of the device and intrinsic limitation of the operation frequency.